 
C     $Id: extra2.F 17 2012-12-07 05:10:30Z wangsl2001@gmail.com $
c
c
c     ###################################################
c     ##  COPYRIGHT (C)  1990  by  Jay William Ponder  ##
c     ##              All Rights Reserved              ##
c     ###################################################
c
c     ############################################################
c     ##                                                        ##
c     ##  subroutine extra2  --  atomwise user defined Hessian  ##
c     ##                                                        ##
c     ############################################################
c
c
c     "extra2" calculates second derivatives of any additional
c     user defined potential energy contribution for a single
c     atom at a time
c
c
      subroutine extra2 (i)
      implicit none
      include 'sizes.i'
      include 'atoms.i'
      include 'hessn.i'
      integer i
c
c
c     compute the Hessian elements for extra energy terms
c
c     do j = 1, n
c        hessx(1,j) = hessx(1,j) + ......
c        hessy(2,j) = hessy(2,j) + ......
c        hessz(3,j) = hessz(3,j) + ......
c     end do
c
      return
      end
